This invention relates to a composition that comprises or is produced from a titanium compound and a phosphorus compound and to a process for esterification, transesterification, or polymerization of a carbonyl compound in the presence of a catalyst composition and a phosphorus compound.
Polyesters such as, for example, polyethylene terephthalate, polytrimethylene terephthalate and polybutylene terephthalate, generally referred to as xe2x80x9cpolyalkylene terephthalatesxe2x80x9d, are a class of important industrial polymers. They are widely used in fibers, films, and molding applications.
Polyesters can be produced by transesterification of an ester such as dimethyl terephthalate (DMT) with a glycol followed by polycondensation or by direct esterification of an acid such as terephthalic acid (TPA) with a glycol followed by polycondensation. A catalyst is used to catalyze the esterification, transesterification and/or polycondensation.
For example, polyester can be produced by injecting a slurry mixture of TPA and glycol at about 80xc2x0 C. into an esterifier. Linear oligomer with degree of polymerization less than 10 are formed in one or two esterifiers at temperatures from 240xc2x0 C. to 290xc2x0 C. The oligomer is then polymerized in one or two prepolymerizers and then a final polymerizer or finisher at temperatures from 250xc2x0 C. to 300xc2x0 C. TPA esterification is catalyzed by the carboxyl groups of the acid.
Antimony is often used. for polymerization or polycondensation reaction. However, antimony forms insoluble antimony complexes that plug fiber spinnerets and leads in fiber spinning to frequent shutdowns to wipe spinnerets clean of precipitated antimony compounds. The antimony-based catalysts are also coming under increased environmental pressure and regulatory control, especially in food contact applications.
Titanium catalysts can be used in the esterification, transesterification, and polycondensation reactions. However, the titanium catalysts tend to hydrolyze on contact with water forming glycol-insoluble oligomeric species, which lose catalytic activity. Polyesters produced from an organic titanate also generate yellow discoloration. Even water compatible titanates, such as titanium bis-ammonium lactate, bis-triethanolamine titanate or the titanium sodium citrate catalysts disclosed in EP 812818, when used as polyesterification catalysts, generate significant yellow discoloration in the resultant polymer. Similarly, WO 99/28033 discloses an organometallic compound for producing an ester. The organometallic compound comprises the reaction product of an orthoester of titanium, zirconium, or aluminum, an alcohol containing at least two hydroxyl groups, an organophosphorus compound, and a base. When used as polyesterification catalyst, however, it was found that the organometallic compound also generates undesirably significant yellow discoloration in the final product.
Therefore, there is an increasing need for developing a new catalyst that is efficient, produces a polymer with reduced color, exhibits good catalytic activity, does not result in plugging fiber spinnerets, and is environmentally friendly.
An advantage of the present invention is the polymer produced using the invention catalyst has improved optical properties (e.g., less undesirable color) compared to polymer produced using an organic titanate catalyst alone. Other advantages will become more apparent as the invention is more ally disclosed herein below.
A composition that can be used for producing polyester is provided, which comprises a titanium compound and a phosphorus compound.
Also provided is a process that can be used for producing polyester, which comprises contacting, in the presence of a catalyst composition and a phosphorus compound, a carbonyl compound and an alcohol in which the composition comprises a titanium compound.
Further provided is a process that can be used to produce a polymer containing reduced insoluble particles or solids, which comprises contacting, in the presence of a catalyst composition and a phosphorus compound in which the catalyst comprises a metal and the phosphorus compound is not phosphoric acid.
The term xe2x80x9creduced insoluble particlesxe2x80x9d or xe2x80x9creduced solidsxe2x80x9d refers to the quantity of insoluble particles or solids present in a polymer such as polyester produced by the invention process as compared to that produced by a conventional process in which phosphoric acid is present in the conventional process.
According to an embodiment of the invention, the invention composition can comprise, consist essentially of, or consists of, or is produced by combining (A) a titanium compound; (B) either (i) a complexing agent and optionally a first solvent or (ii) a combination of a complexing agent, hypophosphorous acid or a salt thereof, and optionally a first solvent, a zirconium compound, or both, or (iii) combinations of (i) and (ii); and (C) a phosphorus compound; and optionally a second solvent.
According to the invention, the preferred titanium compounds used in component (A) are organic titanium compounds such as, for example, titanium tetrahydrocarbyloxides, also referred to as tetraalkyl titanates herein for they are readily available and effective. Examples of suitable titanium tetrahydrocarbyloxides include those having the formula of Ti(OR)4 where each R is individually selected from an alkyl, cycloalkyl, alkaryl, hydrocarbyl radical containing from 1 to about 30, preferably 2 to about 18, and most preferably 2 to 12 carbon atoms per radical and each R can be the same or different. Titanium tetrahydrocarbyloxides in which the hydrocarboxyl group contains from 2 to about 12 carbon atoms per radical which is a linear or branched alkyl radical are most preferred because they are relatively inexpensive, more readily available, and effective in forming the solution. Suitable titanium tetrahydrocarbyloxides include, but are not limited to, titanium tetraethoxide, titanium tetrapropoxide, titanium tetraisopropoxide, titanium tetra-n-butoxide, titanium tetrahexoxide, titanium tetra 2-ethylhexoxide, titanium tetraoctoxide, and combinations of two or more thereof. The titanium tetrahydrocarbyloxides are well known to one skilled in the art. See, for example, U.S. Pat. Nos. 6,066,714 and 6,166,170, the description of which is incorporated herein by reference. Examples of commercially available organic titanium compounds include, but are not limited to, TYZOR(copyright) TPT and TYZOR(copyright) TBT (tetra isopropyl titanate and tetra n-butyl titanate, respectively) available from E. I. du Pont de Nemours and Company, Wilmington, Del., U.S.A.
According to the invention, the titanium tetrahydrocarbyloxide can also be combined with a zirconium compound to produce a mixture comprising a titanium tetrahydrocarbyloxide and a zirconium tetrahydrocarbyloxide. The presently preferred zirconium tetrahydrocarbyloxides include, but are not limited to, zirconium tetraethoxide, zirconium tetrapropoxide, zirconium tetraisopropoxide, zirconium tetra-n-butoxide, zirconium tetrahexoxide, zirconium tetra 2-ethylhexoxide, zirconium tetraoctoxide, and combinations of two or more thereof. The molar ratio of Ti/Zr can be in the range of from about 0.001:1 to about 10:1.
The complexing agent suitable for use in (B)(i) and (B)(ii) can be a hydroxycarboxylic acid, an alkanolamine, an aminocarboxylic acid, or combinations of two or more thereof. It is presently preferred that it be an xcex1-hydroxycarboxylic acid, an alkanolamine, or an xcex1- aminocarboxylic acid in which the hydrocarbyl group or alkyl group has 1 to about 15, preferably 1 to 10 carbon atoms per group, and combinations of two or more thereof. Examples of suitable complexing agents include, but are not limited to, lactic acid, glycolic acid, citric acid, tartaric acid, malic acid, diethanolamine, triethanolamine, tetrahydroxyisopropylethylenediamine, glycine, bis-hydroxyethyl glycine, hydroxyethyl glycine, and combinations of two or more thereof.
For example, TYZOR(copyright) LA is a reaction product produced from a titanium compound and lactic acid, a complexing agent. It is an aqueous solution of titanium bis-ammonium lactate produced by adding two moles of lactic acid to TYZOR(copyright) TPT (tetraisopropyl titanate) followed by addition of water, removal of by-product isopropyl alcohol and neutralization with 28% aqueous ammonium hydroxide solution.
According to the invention, component (B)(ii) can also comprise a hypophosphorous acid or salt thereof having the formula of H2P(O)OM in which M is hydrogen, ammonium ion, a metal ion, or combinations of two or more thereof and the phosphorus atom is bonded to two hydrogen atom. The metal ion can be any metal ion. It is presently preferred that the metal ion be an alkali metal ion. The hypophosphorous acid or its metal salt is commercially available as an aqueous solution and it is generally used herein as an aqueous solution.
According to the invention, the molar ratio of the complexing agent to titanium compound, can be in the range of from about 1:1 to about 10:1, preferably about 1:1 to about 7:1, and most preferably 1:1 to 4:1. The molar ratio of hypophosphorous acid or its salt to titanium compound (P:Ti) can be any ratio that, when the composition is used as catalyst to produce polyester, can reduce the yellowness of the polyester. The preferred ratio can be in the range of from about 0.1:1 to about 10:1, preferably about 0.5:1 to about 7:1, and most preferably 1:1 to 4:1. A solvent can be present in the composition to produce a soluble or substantially soluble composition.
The preferred first solvent can be water or an alcohol having 1 to about 10, preferably 1 to about 8, and most preferably 1 to 5 carbon atoms per molecule such as, for example, an alkylene glycol, a polyalkylene glycol, alkoxylated alcohol, or combinations thereof. Examples of suitable solvents include, but are not limited to, ethanol, propanol, isopropanol, butanol, ethylene glycol, propylene glycol, isopropylene glycol, butylene glycol, 1-methyl propylene glycol, pentylene glycol, diethylene glycol, triethylene glycol, diethylene glycol monomethyl ether, triethylene glycol monomethylether, 2-ethyl hexanol, and combinations of two or more thereof. The preferred second solvent can be the same as the first solvent.
A composition obtained from a titanium compound, a complexing agent, and hypophosphorous acid or salt thereof can be produced by any means known to one skilled in the art such as that disclosed in U.S. Pat. No. 6,166,170, disclosed above.
For component (C), a phosphorus compound that can be used with a titanium-containing catalyst to produce polyester having low yellowness, as compared to a polyester produced from a catalyst without such phosphorus compound can be used. Examples of suitable phosphorus compounds include, but are not limited to, a polyphosphoric acid or a salt thereof, a phosphonate ester, a pyrophosphoric acid or salt thereof, a pyrophosphorous acid or salt thereof, and combinations of two or more thereof. The polyphosphoric acid can have the formula of Hn+2PnO3n+1 in which n is xe2x89xa72. The phosphonate ester can have the formula of (R1O)2P(O)ZCO2R1 in which each R1 can be the same or different and can be independently H, C1-4 alkyl, or combinations thereof, and Z is C1-5 alkylene, C1-5 alkylidene, or combinations thereof, di(polyoxyethylene) hydroxymethyl phosphonate, and combinations of two or more thereof. The salt can be an alkali metal salt, alkaline earth metal salt, ammonium salt, or combinations of two or more thereof.
Illustrative examples of suitable phosphorus compounds include, but are not limited to, potassium tripolyphosphate, sodium tripolyphosphate, potassium tetra phosphate, sodium pentapolyphosphate, sodium hexapolyphosphate, potassium pyrophosphate, potassium pyrophosphite, sodium pyrophosphate, sodium pyrophosphate decahydrate, sodium pyrophosphite, ethyl phosphonate, propyl phosphonate, hydroxymethyl phosphonate, di(polyoxyethylene) hydroxymethyl phosphonate, methylphosphonoacetate, ethyl methylphosphonoacetate, methyl ethylphosphonoacetate, ethyl ethylphosphonoacetate, propyl dimethylphosphonoacetate, methyl diethylphosphonoacetate, triethyl phosphonoacetate, or combinations of two or more thereof. The presently preferred phosphorus compound is tripolyphosphate.
The composition can contain titanium in the range of from about 0.0001% to about 10%, preferably 0.01% to 10%, and most preferably 0.1% to 8% by weight. The composition can contain phosphorous, derived from component (C), such that the P/Ti molar ratio is in the range of about 0.001:1 to about 20:1, preferably about 0.01:1 to about 10:1, and most preferably 0.1:1 to 1:1. Water and a solvent such as a glycol, if present, can make up the rest of the composition.
The invention composition is substantially soluble in a second solvent disclosed above. The term xe2x80x9csubstantiallyxe2x80x9d means more than trivial. It is preferred that the composition be completely soluble in the solvent. However, a substantial portion of the composition can also be suspended or dispersed in the solvent.
The composition can be produced by any means known to one skilled in the art such as those disclosed in U.S. Pat. No. 6,066,714 and U.S. Pat. No. 6,166,170 discussed above and description of which is omitted herein for the interest of brevity.
According to another embodiment of the invention, an esterification, transesterification, or polymerization process can comprise contacting, in the presence of a catalyst composition and a phosphorus compound, a carbonyl compound and an alcohol under a condition sufficient to effect the production of a polymer.
The catalyst composition can be a cobalt, antimony, manganese, or zinc catalyst commonly employed in the manufacture of polyester, description of which is omitted herein because such catalyst is well-known to one skilled in the art. The catalyst composition also can comprise a titanium complex and a phosphorus compound.
The titanium complex can be either a composition comprising, consist essentially of, or consists of, or is produced by combining (A) a titanium compound and (B) either (i) a complexing agent and optionally a first solvent or (ii) a combination of a complexing agent, hypophosphorous acid or a salt thereof, and optionally a first solvent, a zirconium compound, or both, (iii) a combination of a solubility promoter, a phosphorus source, and optionally a first solvent, (iv) a combination of a glycol and optionally a phosphorus compound and water, or (v) combinations of any two of (i), (ii), (iii), and (iv).
The phosphorus compound is the same as that disclosed above in composition component (C), which is incorporated herein.
The definition, scope, and quantity of each of components (A), (B)(i), (B)(ii), and (B)(iv) of the titanium complex are the same as those disclosed above and the descriptions are incorporated herein.
The solubility promoter can be an ortho silicate, ortho zirconate, or combinations thereof. The preferred solubility promoter in (B)(iii) can be an organic silicate, organic zirconate, or combinations thereof. The most preferred solubility promoter can facilitate the dissolution of essentially all titanium present in the composition in a solvent used to prepare the composition, at room temperature (about 25xc2x0 C.). Such solubility promoters include, but are not limited to, organic ortho silicates, organic ortho zirconates, or combinations thereof. The organic ortho silicates have the formula of Si(OR)4 and the organic ortho zirconates have the formula of Zr(OR)4 in which each R is the same as that disclosed above. These solubility promoters are generally commercially available or can be produced by, for example, introducing a silicon tetrachloride or zirconium tetrachloride into a solvent to replace the chlorides with the R groups in the solvent. Examples of suitable solubility promoters include, but are not limited to, tetraethyl ortho silicate, tetra-n-propyl ortho silicate, tetra n-propyl ortho zirconate, tetra n-butyl ortho zirconate, and combinations of two or more thereof. Tetraethyl ortho silicate and tetra-n-propyl ortho silicate are commercially available. Tetra n-propyl ortho zirconate and tetra n-butyl ortho zirconate are organic zirconates commercially available from E. I. du Pont de Nemours and Company under the xe2x80x9cTYZOR(copyright)xe2x80x9d trademark.
The phosphorus source can be a phosphonic acid, a phosphinic acid, a phosphine, or combinations of two or more thereof It is preferred that the phosphorus source in (B)(iii) be selected from a phosphonic acid, a phosphinic acid, a phosphine, or combinations thereof, each of which can have an alkyl, alkenyl, alkaryl, aryalkyl, or aryl group directly bonded to the phosphorus atom. Each group can contain 1 to about 25, preferably 1 to about 20, and most preferably 1 to 15 carbon atoms per group such as methyl group, ethyl group, a phenyl group, or naphthyl group. Furthermore, the hydroxy group of the acid can also be substituted. For example, one or two OH groups bonded to the phosphorus atom of a phosphonic acid can be esterified.
Examples of suitable phosphorus sources include, but are not limited to, phenyl phosphinic acid, diphenyl phosphinic acid and 3-(hydroxyphenylphosphinyl) propanoic acid, 1,2-bis-diphenylphosphinoethane, 1,3-bis-diphenylphosphinopropane, 1,4-bis-diphenylphosphinobutane, bis-4-tolylphosphine oxide, bis-3,5-xylylphosphine oxide, or combinations of two or more thereof.
Component (B)(iii) can further comprise a sulfonic acid or salt thereof can optionally be used in the invention. The preferred sulfonic acids can be any aryl or alkyl sulfonic acid that can be substantially soluble in a solvent disclosed above. Examples of suitable sulfonic acids include, but are not limited to, p-toluene sulfonic acid, benzene sulfonic acid, methane sulfonic acid, ethane sulfonic acid, propane sulfonic acid, butane sulfonic acid, and combinations of two or more thereof. The salt of sulfonic acid can be an alkali metal salt, an alkaline earth metal salt, an ammonium salt, or combinations of two or more thereof.
For component (B)(iv), the glycol can include, but are not limited to, ethylene glycol, propylene glycol, isopropylene glycol, butylene glycol, 1-methyl propylene glycol, pentylene glycol, diethylene glycol, triethylene glycol, and combinations of two or more thereof. The presently preferred glycol is ethylene glycol.
The phosphorus compound for component (B)(iv) can be the same as that disclosed above for composition component (C). The titanium compound, glycol, and optional phosphorus compound ((B)(iv)) and water can be combined, by any means known to one skilled in the art, under a suitable condition effective to the production of the composition or a reaction product. The condition can include a temperature in the range of from about 0xc2x0 C. to about 200xc2x0 C., preferably about 50xc2x0 C. to about 120xc2x0 C., and most preferably 50xc2x0 C. to 80xc2x0 C., under a pressure that can accommodate the temperature range, and for a period of time sufficient to produce the composition or the reaction product. One of the main reaction products is probably titanium glycolate, which can be complexed with the phosphorus compound. For example, the solution of tetraisopropyl titanate /glycol/potassium tripolyphosphate can be heated between 40xc2x0 C. and 200xc2x0 C., preferably between 60xc2x0 C. and 120xc2x0 C., to remove and condense isopropyl alcohol. Based on the total weight of the composition equaling 100%, the titanium complex comprising (B)(iv) can comprise about 0.0001% to about 20%, preferably about 0.001% to about 10% titanium; about 30% to about 99.999%, preferably about 50% to about 99.999% of the composition is derived from a glycol; and about 0.01% to about 50% water. The molar ratio of phosphorus to titanium, if a phosphorous is present in the composition, can be in the range of from about 0.001:1 to about 20:1, preferably about 0.01:1 to about 10:1.
The catalyst composition can further comprise a cocatalyst. Examples of cocatalysts include, but are not limited to, cobalt/aluminum catalysts, antimony compounds, and combinations thereof. The cobalt/aluminum catalyst comprises a cobalt salt and an aluminum compound in which the mole ratio of aluminum to cobalt is in the range of from 0.25:1 to 16:1. The cobalt/aluminum catalyst is disclosed in the U.S. Pat. No. 5,674,801, disclosure of which is incorporated herein by reference.
A preferred antimony compound can be any antimony compound that is substantially soluble in a solvent disclosed above. Examples of suitable antimony compounds include, but are not limited to, antimony oxides, antimony acetate, antimony hydroxides, antimony halides, antimony sulfides, antimony carboxylates, antimony ethers, antimony glycolates, antimony alcoholates, antimony nitrates, antimony sulfates, antimony phosphates, and combinations of two or more thereof.
According to the invention, any carbonyl compound, which when combined with an alcohol, can produce an ester or polyester can be used. Such carbonyl compounds include, but are not limited to, acids, esters, amides, acid anhydrides, acid halides, salts of carboxylic acid oligomers or polymers having repeat units derived from an acid, or combinations of two or more thereof. The presently preferred acid is an organic acid such as a carboxylic acid or salt thereof.
A preferred process for producing an ester or polyester comprises, consists essentially of, or consists of contacting a reaction medium with the catalyst composition disclosed above. The reaction medium can comprise, consist essentially of, or consist of an alcohol and either (1) an organic acid, a salt thereof, an ester thereof, or combinations thereof or (2) an oligomer having repeat units derived from an organic acid or ester.
The organic acid or ester thereof can have the formula of R2COOR2 in which each R2 independently can be (1) hydrogen, (2) hydrocarboxyl radical having a carboxylic acid group at the terminus, or (3) hydrocarbyl radical in which each radical has 1 to about 30, preferably about 3 to about 15 carbon atoms per radical which can be akyl, alkenyl, aryl, alkaryl, aralkyl radical, or combinations of two or more thereof. The presently preferred organic acid or ester thereof has the formula of R2O2CACO2 R2 in which A is an alkylene group, an arylene group, alkenylene group, or combinations of two or more thereof and R2 is the same as above. Each A has about 2 to about 30, preferably about 3 to about 25, more preferably about 4 to about 20, and most preferably 4 to 15 carbon atoms per group. Examples of suitable organic acids include, but are not limited to, terephthalic acid, isophthalic acid, napthalic acid, succinic acid, adipic acid, phthalic acid, glutaric acid, acrylic acid, oxalic acid, benzoic acid, maleic acid, propenoic acid, and combinations of two or more thereof. The presently preferred organic diacid is terephthalic acid because the polyesters produced therefrom have a wide range of industrial applications. Examples of suitable esters include, but are not limited to, dimethyl adipate, dimethyl phthalate, dimethyl terephthalate, methyl benzoate, dimethyl glutarate, and combinations of two or more thereof.
Any alcohol that can esterify an acid to produce an ester or polyester can be used in the present invention. The presently preferred alcohol is an alkylene glycol of the formula (HO)nA(OH)n A and n are the same as those disclosed above. Examples of suitable alcohols include, but are not limited to, ethanol, propanol, isopropanol, butanol, ethylene glycol, propylene glycol, isopropylene glycol, butylene glycol, 1-methyl propylene glycol, pentylene glycol, diethylene glycol, triethylene glycol, 2-ethyl hexanol, and combinations of two or more thereof. The presently most preferred alcohol is an alkylene glycol such as ethylene glycol for the polyester produced therefrom has a wide range of industrial applications.
The oligomer of a carbonyl compound such as TPA and alcohol generally has a total of about 2 to about 100, preferably from about 2 to about 20 repeat units derived from the carbonyl compound and alcohol.
The contacting of the carbonyl compound and alcohol in the presence of the catalyst can be carried out by any suitable means.
Any suitable condition to effect the production of an ester or polyester can include a temperature in the range of from about 150xc2x0 C. to about 500xc2x0 C., preferably about 200xc2x0 C. to about 400xc2x0 C., and most preferably 250xc2x0 C. to 300xc2x0 C. under a pressure in the range of from about 0.001 to about 1 atmosphere for a time period of from about 0.2 to about 20, preferably about 0.3 to about 15, and most preferably 0.5 to 10 hours.
The molar ratio of the alcohol to carbonyl compound can be any ratio so long as the ratio can effect the production of an ester or polyester. Generally the ratio can be in the range of from about 1:1 to about 10:1, preferably about 1:1 to about 5:1, and most preferably 1:1 to 4:1.
The catalyst, expressed as element Co, Sb, Mn, Zn, or Ti, can be present in the range of about 0.001 to about 30,000 ppm of the medium comprising the carbonyl compound and alcohol, preferably about 0.1 to about 1,000 ppm, and most preferably 1 to 100 ppm by weight. A cocatalyst, if present, can be in the range of from about 0.01 to about 1,000 ppm of the reaction medium.
The invention process can also be carried out using any of the conventional melt or solid state techniques and in the presence or absence of a toner compound to reduce the color of a polyester produced. Example of toner compounds include, but are not limit to, cobalt aluminate, cobalt acetate, Carbazole violet (commercially available from Hoechst-Celanese, Coventry, R.I., U.S.A., or from Sun Chemical Corp, Cin., Ohio, U.S.A.), Estofil Blue S-RLS(copyright) and Solvent Blue 45(trademark) (from Sandoz Chemicals, Charlotte, N.C., U.S.A), CuPc Blue (from Sun Chemical Corp, Cincinnati, Ohio, USA). These toner compounds are well known to one skilled in the art and the description of which is omitted herein. The toner compound can be used with the catalyst disclosed herein in the amount of about 0.1 ppm to 1000 ppm, preferably about 1 ppm to about 100 ppm, based on the weight of polyester produced.
The invention process can also be carried out using any of the conventional melt or solid state techniques and in the presence or absence of an optical brightening compound to reduce the yellowness of the polyester produced. Example of optical brightening compounds include, but are not limit to, 7-naphthotriazinyl-3-phenylcoumarin (commercial name xe2x80x9cLeucopure EGMxe2x80x9d, from Sandoz Chemicals, Charlotte, N.C., USA.), 4,4xe2x80x2-bis(2-benzoxazolyl) stilbene (commercial name xe2x80x9cEastobritexe2x80x9d, from Eastman Chemical, Kingsport, Tenn., USA). These optical brightening compounds are well known to one skilled in the art and the description of which is omitted herein. The optical brightening compound can be used with the catalyst disclosed herein in the amount of about 0.1 ppm to 10000 ppm, preferably about 1 ppm to about 1000 ppm, based on the weight of polyester produced.
The polyester produced by the invention process can comprise about 1 to about 200 parts per million by weight (ppm) of titanium and about 1 to about 200 ppm, preferably about 5 to about 100 ppm, of phosphorus.
According to the invention, the phosphorus compound can be present in the reaction medium before, during, or after an organic acid or ester thereof is esterified or transesterified. Similarly, it can be present before, during, or after the polycondensation stage. The phosphorus compound can be used to inhibit the catalytic activity of a titanium-containing catalyst, to reduce the discoloration of polyester produced using a titanium-containing catalyst, or both. The phosphorus compound can be mixed with the catalyst, such as titanium, antimony, manganese, zinc, before the catalyst is introduced to the polyester reaction process. Alternatively, the phosphorous compound can be introduced to the process separately before or after the catalyst is introduced.
For example, in a TPA process disclosed in the BACKGROUND OF THE INVENTION, a titanium catalyst, alone or with other catalyst such as antimony can be used as polycondensation catalyst for an oligomer. Alternatively, a titanium-containing catalyst can be present in the ester exchanger to accelerate transesterification reaction or in the esterifier to accelerate the esterification reaction. Generally, titanium-containing catalyst is more active in polycondensation reaction than in esterification or transesterification. The proper level of titanium-containing catalyst for esterification or transesterification can be an excess level for polycondensation. When titanium-containing catalyst presented in the esterifier or ester exchanger (transesterifier) is an excess for polycondensation, or when polycondensation is intended with a non titanium-containing catalyst such as antimony, part of or all of the titanium catalyst is preferably deactivated or inhibited after esterification or transesterification with a phosphorous compound disclosed above in composition component (C), to avoid discoloration of the polymer.
The titanium-containing catalyst present in the polymer can cause increased degradation and yellowness in the future processing. Part of or all of the titanium catalyst can be deactivated or inhibited after polymerization with a phosphorous compound disclosed above in composition component (C), to avoid discoloration of the polymer.
Similarly, when manganese, zinc, or other catalysts are used as esterification or transesterification catalyst and titanium-containing catalyst is used as polycondensation catalyst, these catalysts can be deactivated by the presence of a phosphorous compound disclosed above in composition component (C).
Furthermore, many packaging materials such as bottle resin require low turbidity in polymer. Antimony and cobalt in combination with phosphoric acid are commonly used for producing polyester for packaging materials. Unfortunately, phosphoric acid reacts with antimony and cobalt to form insoluble solids, which leads to high turbidity. Therefore, a preferred process is introducing a phosphorus compound, which does not react with a metal or metal-containing compound such as antimony and cobalt to form insoluble solids. The phosphorous compound can be the same as disclosed above in component (C). The phosphorus compound can be present before, during, or after the polycondensation.
According to a further embodiment of the invention, a process for producing polyester having reduced insoluble particles or solids is provided. The process can comprise contacting a carbonyl compound, in the presence of a metal or metal compound, with an alcohol. The carbonyl compound and alcohol can be the same as those disclosed above. The metal or metal compound can be a metal or a metal-containing compound including, but not limited to, TiO2, antimony oxide, antimony glycolate, antimony acetate, manganese acetate, zinc oxide, zinc acetate, cobalt acetate, aluminum compound, germanium compound, titanium composition, or combinations of two or more thereof. These metals or metal compounds are well known to one skilled in the art.
In the manufacturing of fibers, phosphoric acid that is commonly used during the manufacturing process reacts with antimony, manganese, cobalt, aluminum, and/or titanium dioxide, to form insoluble particles or solids. The insoluble solids can plug the spinnerets of fiber manufacturers, or polymer filter packs, causing high pack pressure and frequent process shutdown to replace spinnerets or filter packs. Therefore, a preferred process is to introduce a phosphorus compound that does not form solids with the metal or metal-containing compound into the manufacturing process. The phosphorous compound can be the same as that disclosed above in component (C). The phosphorus compound can be present before, during, or after the polycondensation.